1. Field of the Invention
The present invention relates to an automotive air conditioner of heat pump type and an expansion valve used for said automotive air conditioner.
In recent years the combustion efficiency of a vehicle provided with an internal-combustion engine has improved. This makes it hard for the cooling water, used as a heat source, to rise to a temperature required for the heating. At the same time, the utilization rate of an internal-combustion engine is low in a hybrid vehicle equipped with both an internal-combustion engine and an electric motor. This makes it harder for such the cooling water to be utilized. For an electric-powered car, there is no heat source coming from any internal-combustion engine at all. For this reason, proposed is an automotive air conditioner of heat pump type (see Patent Document 1, for instance). In this proposed automotive air conditioner of heat pump type, a cycle operation using a refrigerant is carried out not only for the cooling but also for the heating, and a vehicle's passenger compartment can be dehumidified and heated.
Such an automotive air conditioner as described above employs a refrigeration cycle including a compressor, an external heat exchanger, an evaporator, an internal heat exchanger and so forth. The functions of the external heat exchanger are switched between when the air conditioner is in a heating operation and when it is in a cooling operation. At the time the air conditioner is in a heating operation, the external heat exchanger functions as an evaporator. At this time, the internal heat exchanger radiates heat in a process where the refrigerant circulates in the refrigeration cycle, and the thus radiated heat heats air inside the passenger compartment. At the time the air conditioner is in a cooling operation, the external heat exchanger functions as a condenser. At this time, the refrigerant condensed by the external heat exchanger is evaporated by the evaporator and, the evaporative latent heat cools the air of the interior of the vehicle. In so doing, the air in the passenger compartment is also dehumidified.